1. Field of the Invention
Embodiments of the present invention relate generally to surgical repair of the rotator cuff tendon and, more particularly, to devices and methods used in repairing the rotator cuff tendon that has been detached from the humeral head.
2. Description of the Related Art
In surgeries involving repair of a rotator cuff tendon that has been detached from the humeral head, the tendon must be artificially pressed against the humeral head in order to allow the tendon to naturally re-attach to the underlying bone over time. FIGS. 1 and 2 illustrate two prior art techniques for repairing a rotator cuff tendon that has been detached from the humeral head.
FIG. 1 schematically illustrates a rotator cuff tendon 101 secured to a humeral head 102 of a humerus 100 by a plurality of suture anchors 103. Suture anchors 103 are positioned so that sutures 104, which are sewn into rotator cuff tendon 101, position the tendon against region 105 of humeral head 102, where region 105 approximates the original anatomic attachment region of rotator cuff tendon 101, often referred to as the “footprint.” In this way, rotator cuff tendon 101 will grow onto region 105, forming a new bond between rotator cuff tendon 101 and humeral head 102. Issues associated with the use of the technique illustrated in FIG. 1 include anchor displacement, “lift-off” of the rotator cuff tendon, the availability of a limited number of sutures to secure rotator cuff tendon 101 to humeral head 102, and the inability to perform this surgery because rotator cuff tendon 101 has retracted too far away from the original anatomic attachment location of rotator cuff tendon 101.
The bone making up humeral head 102 near the footprint of the rotator cuff provides a relatively weak base for the insertion of suture anchors 103, since this portion of humerus 100 is relatively porous and soft. Because of this, adequate fixation of suture anchors 103 is problematic. Namely, anchor displacement from the supporting bone is a common failure mechanism of suture anchors 103, and results from localized fracturing of the surrounding bone material.
Suture anchors 103, when positioned as shown, hold rotator cuff tendon 101 against region 105. However, when the arm containing humerus 100 is raised, “lift-off” of rotator cuff tendon 101 from region 105 may occur, i.e., rotator cuff tendon 101 is temporarily pulled out of contact with region 105. Lift-off is known to inhibit the re-attachment and healing of rotator cuff tendon 101.
The number of suture anchors that can be used is limited. This is due to the limited area of humeral head 102 in which suture anchors 103 are placed. Also, the placement of many suture anchors 103 is time consuming and tedious for the surgeon. As a consequence, a small number of larger sutures are typically used with suture anchors, leading to very large knot volumes. Very large knot volumes result because the knot volume of a suture is roughly proportional to the cube of the suture diameter. Large knots on the surface of the rotator cuff are undesirable as they rub against the overlying acromial bone. Furthermore, fewer sutures provide a less robust connection between rotator cuff tendon 101 and humeral head 102. For a given surgical application, a large number of small diameter sutures are superior to a few large sutures, in terms of holding power in the tissue.
In some situations, bone tunnels may be used to attach sutures to bone and thereby properly position a tendon to be repaired. FIG. 2 schematically illustrates a bone tunnel 203 formed through a humeral head 202 of a humerus 200 after removal of bone material from the humeral head 202. Bone tunnel 203 is formed so that sutures 204, which are sewn into rotator cuff tendon 201, may be threaded through holes formed in a bone structure 206 and thereby position rotator cuff tendon 201 against region 205 for proper healing. A key limitation of this technique is that an already weak bone structure 206 is further weakened as a result of thread holes formed for sutures 204 and is susceptible to breakage before rotator cuff tendon 201 is sufficiently healed.